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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 8 |
| 3 | 50 |
| 4 | 336 |
| 5 | 2418 |
| 6 | 18088 |
| 7 | 138850 |
| 8 | 1086016 |
| 9 | 8617122 |
| 10 | 69159896 |
| 11 | 560290322 |
| 12 | 4574820624 |
| 13 | 37603654098 |
| 14 | 310873702392 |
| 15 | 2582964183874 |
| 16 | 21556333188288 |
| 17 | 180609299685954 |
| 18 | 1518572497996568 |
| 19 | 12808849866774002 |
| 20 | 108351496132761104 |
| 21 | 918964407713589618 |
| 22 | 7812768025080427672 |
[2,8,50,336,2418,18088,138850,1086016,8617122, 69159896,560290322,4574820624,37603654098, 310873702392,2582964183874,21556333188288, 180609299685954,1518572497996568, 12808849866774002,108351496132761104, 918964407713589618,7812768025080427672] |